Abstract A159: Agonistic CD40 antibody therapy induces formation of tertiary lymphoid structures in glioma and inhibits the response to immune-checkpoint blockade

Cancer immunotherapy of glioma, the most common primary brain tumor in adults, is constrained by an immunosuppressive microenvironment. Tertiary lymphoid structures (TLSs) are ectopic lymphoid structures that mediate immune responses and provide a local site for tumor antigen presentation. Here, we show for the first time that TLSs are present in human low-grade glioma and that they can be induced in murine glioma models. Agonistic CD40 antibodies induced lymphotoxin α expression in B cells and enhanced the formation of TLSs in mice bearing orthotopic GL261 or CT-2A gliomas. TLSs consisting of B cells, T-cells and antigen presenting cells formed around CD31+ vessels proximal to the tumor tissue and adjacent to the meninges. Agonistic CD40 antibody treatment improved the CD8+ T-cell / Treg ratio in tumor-bearing mice, but there was no survival benefit. A decreased CD69 activation status on CD8+ T-cells, an increase of B cells with a CD1d+CD5+ regulatory phenotype and a high infiltration of Tregs in TLSs indicate that agonistic CD40 antibodies induce an immunosuppressive microenvironment in glioma. Consistent with this, the efficacy of both PD-1 and CTLA-4 checkpoint blockade was significantly decreased by co-administration of agonistic CD40 antibodies. These results demonstrate that TLSs are present and can be induced in glioma, but that they at least under certain conditions are associated with immunosuppression, shedding light on new mechanisms of immune regulation in the brain microenvironment. Citation Format: Luuk van Hooren, Alessandra Vaccaro, Maria Georganaki, Mohanraj Ramachandran, Hua Huang, Joey Lau, Anja Smits, Magnus Essand, Anna Dimberg. Agonistic CD40 antibody therapy induces formation of tertiary lymphoid structures in glioma and inhibits the response to immune-checkpoint blockade [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr A159.